Contourites offshore Pantelleria Island (Sicily Channel, Mediterranean Sea): depositional, erosional and biogenic elements

摘要

High-resolution seismic reflection profiles and multibeam bathymetry data collected in 2006 and 2008 around Pantelleria Island show the widespread occurrence of contourite drifts and erosional elements ～30 km from the narrowest part (～145 km) of the Sicily Channel, where water masses from the Eastern Mediterranean flow towards the Western Mediterranean. The contourite drifts are rather small (up to 10 km long and 3.3 km wide), at water depths of ～250–750 m. Most are elongated separated drifts with quite well-developed moats and crests, aligned roughly parallel to the regional bathymetric contours. Erosional elements include abraded surfaces, moats, scours and subcircular depressions. In addition, a wide sector of the seafloor adjacent to a seamount located SW of Pantelleria Island is characterized by numerous biogenic build-ups colonized by deep-water corals (Madrepora oculata). The spatial distribution of sediment drifts, erosional features and biogenic build-ups suggests an origin from a northwestward- flowing bottom current, in this case the outflow of Levantine Intermediate Water and transitional Eastern Mediterranean Deep Water via the Sicily Channel. These findings for the Pantelleria offshore sector demonstrate that contourite processes are able to concentrate a high variety of closely spaced depositional and erosional features even in small areas (in this case, about 2,000 km~2). This Pantelleria focusing can plausibly be related to a particular configuration of the prevailing bottom-current regime in complex interaction with an uneven bathymetry shaped mainly by tectonic and volcanic activity. The distribution of bottom currents seems to be strongly influenced by morphological features ranging from major seabed obstacles, such as the Pantelleria volcanic complex and the so-called southwest seamount, to smaller-scale escarpments and banks. This is consistent with previous findings for Mediterranean and other settings characterized by neotectonics and large topographic features.